TWI883781B - Touch sensing device and touch sensing method - Google Patents

Abstract

A touch sensing device and a touch sensing method are provided. The touch sensing device includes a reference voltage generator, a switch, a charge storage device, a touch panel sensor and at least one circuit component. The reference voltage generator provides the reference voltage. The reference voltage is obtained by one end of the switch. The charge storage device is coupled to another end of the switch. The circuit element is coupled to the touch panel sensor, and a reference voltage end of the circuit element is coupled to the charge storage device. The switch is turned on during a first period to provide the reference voltage to the charge storage device, wherein the charge storage device temporarily stores a voltage level of the reference voltage as a first voltage level. The switch is turned off during the second period, wherein the touch panel sensor and the circuit component perform the touch sensing function according to the first voltage level temporarily stored in the charge storage device.

Description

Touch sensing device and touch sensing method

The present invention relates to a reference voltage transmission technology in touch sensing, and in particular to a touch sensing device and a touch sensing method.

Consumer electronic devices often use touch panels and corresponding touch sensing technology as one of the means of inputting information. However, today's touch sensing technology is very susceptible to external noise or noise when the physical characteristics of circuit components are non-ideal. Therefore, in order to improve the signal-to-noise ratio (SNR), it is necessary to suppress various noises on the touch panel.

Noise on the touch panel often occurs during transmission between components. For example, the reference voltage generator transmits the reference signal to each component on the touch panel, but it also transmits the noise along with the reference signal to the aforementioned components, causing the aforementioned components to be affected by the noise. Therefore, how to reduce or suppress the noise on the touch panel is one of the problems to be solved when designing a touch panel.

The present invention provides a touch sensing device and a touch sensing method, which temporarily stores a reference signal in a charge storage device to prevent other noises from affecting the temporarily stored reference signal, and uses a digital filter to eliminate the influence of DC noise to improve the signal-to-noise ratio (SNR) in a display panel or a corresponding display device.

The touch sensing device of the embodiment of the present invention includes a reference voltage generator, a switch, a charge storage device, a touch panel sensor and at least one circuit element. The reference voltage generator is used to provide a reference voltage. One end of the switch is coupled to the reference voltage generator to obtain the reference voltage. The charge storage device is coupled to the other end of the switch. At least one circuit element is coupled to the touch panel sensor and the reference voltage end of the circuit element is coupled to the charge storage device. The switch is turned on in a first period so that the reference voltage of the reference voltage generator is provided to the charge storage device, wherein the charge storage device temporarily stores the voltage level of the reference voltage as a first voltage level. The switch is turned off during the second period, wherein the touch panel sensor and the at least one circuit element perform a touch sensing function according to the first voltage level temporarily stored in the charge storage device.

The touch sensing method of the embodiment of the present invention is applied to a touch sensing device. The touch sensing device includes a reference voltage generator, a touch panel sensor, at least one circuit element, a switch, and a charge storage device coupled to the at least one circuit element. The touch sensing method includes the following steps. In a first period, the switch is turned on so that the reference voltage provided by the reference voltage generator is provided to the charge storage device, wherein the charge storage device temporarily stores the voltage level of the reference voltage as a first voltage level. And, in a second period, the switch is turned off, wherein the touch panel sensor and the at least one circuit element perform a touch sensing function according to the first voltage level temporarily stored by the charge storage device.

Based on the above, the touch sensing device and touch sensing method of the embodiment of the present invention utilizes a switch to temporarily store a reference signal in a charge storage device, so that the noise becomes a DC offset noise. Then, the temporarily stored reference signal is provided to a circuit element to perform a corresponding function. In addition to utilizing switches and corresponding timings to prevent other noises (e.g., noise transmitted from a terminal coupled to a reference voltage generator) from continuously affecting the reference signal received by the aforementioned circuit element, the embodiment of the present invention also utilizes a digital filter to eliminate the influence of the DC offset noise, so as to maintain or improve the signal-to-noise ratio (SNR) in a display panel or a corresponding display device. The embodiment of the present invention uses switches and charge storage devices to replace the previous resistor-capacitor circuit, which can effectively reduce the layout area of the circuit.

100, 200: Touch sensor device

110, 210: Touch panel sensor

120, 220: Reference voltage generator

131, 231: Transmission circuit

132, 232, LDO: low voltage dropout regulator

133, 233: Receiver circuit

134, 234, ADC: Analog-to-digital converter

141~143: Filter

251~253: Charge storage device

S410~S440: Steps of touch sensing method

R: Resistance

C, C1: Capacitor

Vref, Vref1~Vref3, Vref21-Vref23: reference voltage

SW1-SW3: switch

SSW: Switching signal

T1: First period

T2: The second period

T21: Touch sensing function period

T22: Digital processing period

Figure 1 is a circuit diagram of a touch sensing device in the prior art.

Figure 2 is a circuit diagram of a touch sensing device according to an embodiment of the present invention.

Figure 3 is a schematic diagram of a digital filter performing digital processing on a touch sensing signal in an embodiment of the present invention.

Figure 4 is a flow chart of a touch sensing method according to an embodiment of the present invention.

Figure 5 is a first timing diagram of the touch sensing method in an embodiment of the present invention.

Figure 6 is a second timing diagram of the touch sensing method in an embodiment of the present invention.

FIG1 is a circuit diagram of a touch sensing device 100 of the prior art. FIG1 touch sensing device 100 includes a touch panel sensor 110, a reference voltage generator 120, and multiple circuit elements matching the touch panel sensor 110 (including but not limited to a transmission end circuit 131, a low voltage difference regulator (LDO) 132, a receiving end circuit 133, an analog-to-digital converter (ADC) 134, etc.). FIG1 reference voltage generator 120 provides a reference voltage Vref to each circuit element to prepare for the touch panel sensor 110 and these circuit elements to perform a touch sensing function.

It is particularly noted that the voltage value of the reference voltage Vref required by each circuit element may not be the same, that is, the voltage values corresponding to the reference voltage Vref1 corresponding to the transmission end circuit 131, the reference voltage Vref2 corresponding to the LDO 132, and the reference voltage Vref3 corresponding to the receiving end circuit 133 and the ADC 134 may be different.

As shown in FIG. 1 , the reference voltage Vref of FIG. 1 has accompanying noise. In order to improve the efficiency of electronic components (such as the transmission circuit 131, LDO 132, ADC 134, etc.), it is necessary to provide a reference voltage with low noise. Therefore, filters 141~143 (such as resistor-capacitor filters) for reducing noise are set at the reference voltage end of the circuit element to reduce the noise in the reference voltage Vref1~Vref3. However, the resistor R and the capacitor C will occupy a larger layout area of the circuit and cannot completely filter out the noise. LDO 132 and receiving circuit 133 have a greater impact on noise, so the power supply voltage rejection ratio (PSRR) should also be taken into consideration during circuit design.

FIG2 is a circuit diagram of a touch sensing device 200 according to an embodiment of the present invention. In an embodiment of the present invention, switches SW1~SW3 and charge storage devices 251~253 are used to replace filters 141~143 in the touch sensing device 200. In addition to using switches SW1~SW3 and corresponding timing to prevent other noises from continuously affecting the reference signals Vref21~V23 received by the circuit elements, digital filters are also used to eliminate the influence of DC offset noise to maintain or improve the signal-to-noise ratio (SNR) in the display panel or the corresponding display device.

In detail, the touch sensing device 200 includes a reference voltage generator 220, a switch (e.g., switches SW1-SW3 in FIG. 2 ), a charge storage device (e.g., charge storage devices 251-253 in FIG. 2 ), a touch panel sensor 210, and at least one circuit element matched with the touch panel sensor 210 (e.g., but not limited to, a transmission end circuit 231, an LDO 232, a receiving end circuit 233, and an ADC 234). The reference voltage generator 220 is used to provide a reference voltage Vref. The reference voltage generator 220 may be a bandgap reference circuit. The reference voltage Vref of this embodiment may include accompanying noise. One end of the switches SW1~SW3 is coupled to the reference voltage generator 220 to obtain the reference voltage Vref. The charge storage devices 251~253 are respectively coupled to the other ends of the corresponding switches SW1~SW3. The circuit elements are directly or indirectly coupled to the touch panel sensor 210 and the reference voltage ends of these circuit elements are respectively coupled to the corresponding charge storage devices 251~253.

The switches SW1~SW3 are turned on in the first period. Thus, the reference voltage Vref of the reference voltage generator 220 is provided to the corresponding charge storage devices 251~253. The charge storage devices 251~253 temporarily store the voltage level of the reference voltage Vref as the first voltage level. For example, the charge storage device 251 temporarily stores the voltage level of the reference voltage Vref during the first period as the first voltage level of the reference voltage Vref21; the charge storage device 252 temporarily stores the voltage level of the reference voltage Vref during the first period as the first voltage level of the reference voltage Vref22; the charge storage device 253 temporarily stores the voltage level of the reference voltage Vref during the first period as the first voltage level of the reference voltage Vref23.

The switches SW1-SW3 are turned off in the second period so that the reference voltage Vref of the reference voltage generator 220 is not provided to the charge storage devices 251-253. At this time, the charge storage devices 251-253 should have temporarily stored the first voltage level of the reference voltage Vref21-Vref23, and the first voltage level includes the ideal voltage level of the reference voltage Vref and the DC bias as noise. In the second period, the touch panel sensor 210 and the at least one circuit element perform the touch sensing function of the embodiment of the present invention according to the first voltage level temporarily stored by the corresponding charge storage devices 251-253. After the touch sensing function is executed, an analog touch sensing signal can be generated. In other words, the noise provided by the reference voltage generator 220 is a fixed-value DC bias noise without frequency jitter. This DC bias noise will not affect the performance of the aforementioned electronic components (such as the transmission circuit 231, LD0 232, the receiving circuit 233 or ADC 234) when they are operating, so that the touch sensing device 200 can achieve a higher SNR as a whole.

The touch sensing device 200 also includes a digital filter. The digital filter can be a bandpass filter or a finite impulse response (FIR) filter. The digital filter can receive and process the aforementioned analog touch sensing signal to generate a digital touch sensing signal. The DC bias noise in the reference voltage is filtered by the digital filter to eliminate the influence of the noise in the analog touch sensing signal.

The charge storage devices 251-253 of this embodiment can be implemented by capacitors C1, and the capacitance value of the capacitors C1 in the charge storage devices 251-253 is smaller than the capacitance value of the capacitors C in the R-C circuits 141-143 in FIG. 1, which can reduce the circuit layout area. For example, the capacitance value of the capacitor C1 in FIG. 2 is not greater than 1pF, and can be approximately 1pF or even less than 1pF, while the capacitance value of the capacitor C in FIG. 1 is much greater than 1pF, for example, more than 10pF.

FIG3 is a schematic diagram of a digital filter digitally processing a touch sensing signal in an embodiment of the present invention. FIG3 shows the waveform of the digital touch sensing signal after digital processing by the digital filter, the horizontal axis of FIG3 is the frequency, and the vertical axis of FIG3 is the signal strength (voltage). It can be seen from FIG3 that the digital touch sensing signal is mainly an AC signal, which can filter out the DC bias noise in the reference voltage (as shown by the arrow 310 in FIG3). It is particularly noted that the arrow 310 is not part of the waveform of the digital touch sensing signal, but is only used to illustrate that the DC bias noise of the reference voltage is filtered by the digital filter.

FIG4 is a flow chart of a touch sensing method 400 of an embodiment of the present invention. The touch sensing method 400 of FIG4 can be applied to the circuit structure of the touch sensing device 200 of FIG2. The touch sensing method 400 of FIG4 of this embodiment can be an overall step of executing a touch sensing function. In step S410, in a first period, the switches SW1~SW3 of FIG2 are controlled from off to on, so that the reference voltage Vref provided by the reference voltage generator 220 of FIG2 is provided to the corresponding charge storage devices 251~253. The charge storage devices 251~253 respectively temporarily store the voltage level of the reference voltage Vref as the first voltage level of the reference voltage Vref21~Vref23. In step S420, in the second period, SW1~SW3 are controlled from on to off. At this time, the touch panel sensor 210 in Figure 2 and the aforementioned circuit elements perform a touch sensing function according to the first voltage level of the reference voltages Vref21~Vref23 temporarily stored in the charge storage devices 251~253. After the touch sensing function is executed, an analog touch sensing signal is generated.

In step S430, the digital filter receives and processes the analog touch sensing signal generated by the touch sensing function to generate a digital touch sensing signal. The DC bias noise in the reference voltage is filtered by the digital filter. In step S440, wait for the start of the next touch sensing function. For other detailed operations of the touch sensing method 400 of FIG. 4, refer to other embodiments.

FIG. 5 is a first timing diagram of a touch sensing method in an embodiment of the present invention. The first period T1 in FIG. 5 is used to execute step S410 in FIG. 4 , and the second period T2 in FIG. 5 is used to execute step S420 and step S430 in FIG. 5 . The switching signal SSW is used to control the on or off of switches SW1~SW3. The switches SW1~SW3 of this embodiment are on (i.e., both ends of the switch are on) when the switching signal SSW is enabled (e.g., logical "1"), and are off (i.e., both ends of the switch are off and cut off) when the switching signal SSW is disabled (e.g., logical "0"). Step S420 corresponds to the touch sensing function period T21 in FIG. 5 . Step S430 corresponds to the digital processing period T22 in FIG5 . The first period T1 and the second period T2 in FIG5 can be collectively referred to as a complete cycle of the touch sensing function in this embodiment.

FIG. 6 is a second timing diagram of the touch sensing method in an embodiment of the present invention. FIG. 6 is different from FIG. 5 in that after step S410 of FIG. 4 is executed in the first period T1 in FIG. 6, step S420 and step S430 corresponding to the second period T2 are executed twice. Step S410 of FIG. 4 is used to turn on the switch so that the charge storage devices 251-253 of FIG. 2 can update or maintain the first voltage level of the reference voltages Vref21-Vref23. If the design of the charge storage devices 251-253 in FIG. 2 is good and can keep the first voltage level of the reference voltages Vref21-Vref23 unchanged for a long time, then step S410 in FIG. 4 executed in the first period T1 in FIG. 6 can be executed once, and then step S420 and step S430 corresponding to the second period T2 can be executed multiple times.

In summary, the touch sensing device and touch sensing method of the embodiment of the present invention utilize switches to temporarily store the reference signal in the charge storage device, so that the noise becomes DC offset noise. Then, the temporarily stored reference signal is provided to the circuit element to perform the corresponding function. In addition to utilizing switches and corresponding timings to prevent other noises (e.g., noise transmitted from the terminal coupled to the reference voltage generator) from continuously affecting the reference signal received by the aforementioned circuit element, the embodiment of the present invention also utilizes a digital filter to eliminate the influence of the DC offset noise, so as to maintain or improve the signal-to-noise ratio (SNR) in the display panel or the corresponding display device. The embodiment of the present invention uses switches and charge storage devices to replace the previous resistor-capacitor circuit, which can effectively reduce the layout area of the circuit.

Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Any person with ordinary knowledge in the relevant technical field may make some changes and modifications within the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of the patent application attached hereto.

200: Touch sensor device

210: Touch panel sensor

220: Reference voltage generator

231: Transmission circuit

232. LDO: Low voltage dropout regulator

233: Receiver circuit

234. ADC: Analog-to-digital converter

251-253: Charge storage device

C1: Capacitor

Vref, Vref21-Vref23: reference voltage

SW1-SW3: switch

Claims (11)

A touch sensing device comprises: A reference voltage generator for providing a reference voltage; A switch, one end of which is coupled to the reference voltage generator to obtain the reference voltage; A charge storage device, which is coupled to the other end of the switch; A touch panel sensor; and At least one circuit element, which is coupled to the touch panel sensor and the reference voltage end of the circuit element is coupled to the charge storage device, wherein the switch is turned on in a first period so that the reference voltage of the reference voltage generator is provided to the charge storage device, wherein the charge storage device temporarily stores the voltage level of the reference voltage as a first voltage level, The switch is turned off in the second period, wherein the touch panel sensor and the at least one circuit element perform a touch sensing function according to the first voltage level temporarily stored in the charge storage device, wherein the first voltage level is the DC voltage level of the reference voltage and the DC bias of the noise. A touch sensing device as described in claim 1, wherein the touch sensing function generates an analog touch sensing signal after being executed, and the touch sensing device further comprises: a digital filter, which receives and processes the analog touch sensing signal to generate a digital touch sensing signal, wherein the DC bias noise in the reference voltage is filtered out by the digital filter. A touch sensing device as described in claim 2, wherein the digital filter is a bandpass filter or a finite pulse impulse response filter. A touch sensing device as described in claim 1, wherein the charge storage device includes a capacitor, wherein the capacitance value of the capacitor is not greater than 1pF. A touch sensing device as described in claim 1, wherein the at least one circuit element is one of a transmitting end circuit, a receiving end circuit, a low voltage difference regulator, an analog-to-digital converter, or a combination thereof. A touch sensing device as described in claim 1, wherein the touch sensing function of the second period is executed multiple times after the first period is executed. A touch sensing method is applied to a touch sensing device, the touch sensing device comprising a reference voltage generator, a touch panel sensor, at least one circuit element, a switch and a charge storage device coupled to the at least one circuit element, the touch sensing method comprising: During a first period, turning on the switch so that a reference voltage provided by the reference voltage generator is provided to the charge storage device, wherein the charge storage device temporarily stores a voltage level of the reference voltage as a first voltage level; and During a second period, turning off the switch, wherein the touch panel sensor and the at least one circuit element perform a touch sensing function according to the first voltage level temporarily stored by the charge storage device, The first voltage level is the DC voltage level of the reference voltage and the DC bias of the noise. The touch sensing method as described in claim 7 further comprises: During the second period, processing the analog touch sensing signal generated by the touch sensing function to generate a digital touch sensing signal, wherein the DC bias noise in the reference voltage is filtered by the digital filter. A touch sensing method as described in claim 7, wherein the charge storage device includes a capacitor, wherein the capacitance value of the capacitor is not greater than 1pF. A touch sensing method as described in claim 7, wherein the at least one circuit element is one of a transmitting end circuit, a receiving end circuit, a low voltage difference regulator, an analog-to-digital converter, or a combination thereof. A touch sensing method as described in claim 7, wherein the touch sensing function of the second period is executed multiple times after the first period is executed.

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